It has become a standard of the industry as to carbide-tipped circular saw blades blanked from steel stock, that the blade surface be polished or sanded to look shiny and to display annular "grind lines", characteristics which potential customers at the point of sale have taken to indicate high quality. Thus the visual appearance of a saw blade at retail has become very important. A manufacturing operation which creates an appearance problem is the act of brazing the carbide tips onto the saw blade teeth. This leaves permanent discolorations in the planar surfaces of the blade adjacent the carbide tips, such that the blade could not be sold in that condition. One solution was to paint the entire surface of the blade, including the teeth and tips. The discoloration was covered, but the carbide tips became indistinguishable from the rest of the blade. Now potential purchasers perceived the blade merely to be a cheap, plain steel blade and not worth the prices charged for carbide. As a result, painted carbide blades don't sell well. The next solution was to carefully mask the major part of the blade to preserve its polished look and sand-blast or shot-blast a narrow band around the rim to remove the discolorations. Inasmuch as carbide tips maintain a visual identity after blasting which is separate from that of the blasted metal rim, the tips were readily perceptible by a prospective purchaser at the point of sale, and the blades did sell. The appearance of a shiny blade with a sandblasted rim thus became the standard of the industry and has been the practice for more than 30 years.
Sandblasting circular saw blades causes the blasted surface to "grow", which in turn causes the blade to warp or bend. Accordingly, it was necessary to securely clamp the blade between two big washer-like plates or masks so that only the rim was exposed and the rest of the saw blade remained shiny, and so that the tendency to distort was inhibited. The other arrangement that inhibited distortion was also to blast both the upper and the lower flat rim surfaces simultaneously with opposed nozzles oriented such that the upper and lower blast streams were equal and opposite. The balanced forces acting on the blade rim tended to "grow" both the upper and lower surfaces substantially equally. The blade was also rotated during the blasting operation to achieve a fairly uniform appearance of the narrow blast band.
From time to time, the subject has come up of blasting substantially the entire planar surface area of the blade. It has been regularly dismissed out of hand, for two main reasons. One was the long-held paradigm that unless the blades had the classic polished or ground look, they wouldn't sell. The other was the conviction that under known methods, it simply wasn't technically sound to sandblast the entirety of the blade--it would surely warp. Using the known process was out of the question because the clamping plates covered the blade. An attempt was made at sandblasting without plates, by blasting one side at a time. The attempt failed because sequential blasting also warped the blade. This consequence further reinforced the belief that blades sandblasted over all or substantially all of their planar surfaces simply were not feasible.